DIY yurt center ring any ideas...?

[ljamies1]

Im starting to plan out my crown/

center ring

for a 30 ft. yurt and would love any/ all suggestions. I am brainstorming ideas/ materials other than wood. Maybe an old flour mill cog wheel or an old cool tractor wheel rim and then either cut female holes around the edge of that to fit the male pin on the raters into. Or instead of cutting holes I could weld on females pieces to the outside edge of the crown to hook the male rafter pins into...any thoughts on other round/ recyclable/ sturdy/ somewhat light weight objects? Since I am making my own cover and rafters, I have the luxury of first locating a crown piece and cutting all other components to size